File Photo: Overdose rescue kits sit on a table during an Opioid Overdose Prevention Training class provided by Lourdes Hospital in Binghamton, New York, U.S., April 5, 2018. (Xinhua/REUTERS)

WASHINGTON, Feb. 22 (Xinhua) -- A new study showed that opioid-related deaths in the United States increased fourfold in the last two decades and spread rapidly in eastern states of the country.

The study published on Friday in the journal JAMA Network Open found that opioid deaths caused by synthetic like fentanyl had outnumbered heroin deaths.

Researchers from Stanford University, Harvard University and the University of Toronto traced the three-stage evolution of opioid crisis. The first wave of opioid-related deaths from the 1990s until about 2010 was linked with prescription painkillers and the second one starting from 2010 was linked with heroin-related deaths.

The third wave began around 2013 and saw a rapid increase in deaths associated with illicitly manufactured synthetic opioids, such as tramadol and fentanyl, according to the study.

They found that a wider range of populations were affected, with the spread of the epidemic from rural to urban areas.

Also, the Centers for Disease Control and Prevention (CDC) reported that African-Americans experienced the largest increase in opioid overdose deaths from 2016 to 2017, with a 26 percent surge.

On average, 130 Americans died every day from an opioid overdose in 2017, according to CDC.

The mortality rate from opioids has increased the fastest in the Washington, D.C., more than tripling every year since 2013, while Florida and Pennsylvania saw their opioid-related mortality rates doubling every two years, according to the study.